1. Field of the Invention
The invention is in the field of devices and methods for radio frequency identification (RFID) and electronic article surveillance (EAS).
2. Description of the Related Art
Radio frequency identification (RFID) tags and labels (collectively referred to herein as “devices”) are widely used to associate an object with an identification code. RFID devices generally have a combination of antennas and analog and/or digital electronics, which may include for example communications electronics, data memory, and control logic. For example, RFID tags are used in conjunction with security locks in cars, for access control to buildings, and for tracking inventory and parcels.
As noted above, RFID devices are generally categorized as labels or tags. RFID labels are RFID devices that are adhesively or otherwise have a surface attached directly to objects. RFID tags, in contrast, are secured to objects by other means, for example by use of a plastic fastener, string or other fastening means.
RFID devices include active tags and labels, which include a power source, and passive tags and labels, which do not. In the case of passive devices, in order to retrieve the information from the chip, a “base station” or “reader” sends an excitation signal to the RFID tag or label. The excitation signal energizes the tag or label, and the RFID circuitry transmits the stored information back to the reader. The RFID reader receives and decodes the information from the RFID tag. In general, RFID tags can retain and transmit enough information to uniquely identify individuals, packages, inventory and the like. RFID tags and labels also can be characterized as to those to which information is written only once (although the information may be read repeatedly), and those to which information may be written during use. For example, RFID tags may store environmental data (that may be detected by an associated sensor), logistical histories, state data, etc.
As the name implies, electronic article surveillance (EAS) is concerned with the embedding or attaching of a security label or tag to a retail item to deter shoplifting. Conventional EAS devices or tags include a resonator that, when activated, causes an alarm to sound when the EAS tag is brought within operative proximity of detection apparatus (which is typically located at the exit of a store). However, if the EAS device is active, a similar signal will also be produced each time that a customer either properly removes purchased goods from the store or enters another store with similar detection apparatus. Generally, EAS tags are inexpensive and disposable items that are not removed from merchandise during check out (which is generally true for RFID tags as well). For these reasons, a variety of different techniques have been developed to deactivate EAS tags, typically by a clerk during check out using deactivation apparatus that needs no physical contact with the tag.
Various types of EAS devices and deactivation systems make use of specially configured tags or labels in connection with an apparatus for positively deactivating such tags or labels. A first example is the EAS tag described in U.S. Pat. No. 4,498,076 to Lichtblau. The Lichtblau tag is provided with a resonant circuit having a capacitor portion with an indentation that permits the resonant circuit to be deactivated according to methodology as described in U.S. Pat. No. 4,728,938 to Kaltner, for example. The Lichtblau EAS tag is readily deactivated at the point of sale by subjecting the tag or label to a relatively high-powered signal which, because of the mechanical indentation, is sufficient to cause a short circuit within the tag or label for deactivation.
Another type of EAS tag, sometimes called a magnetomechanical EAS tag, uses the technology disclosed in U.S. Pat. No. 3,765,007 to Elder. Magnetomechanical tags include an active element and a bias element. When magnetized, the bias element applies a bias magnetic field to the active element which causes the active element to be mechanically resonant at a predetermined frequency upon exposure to an interrogation signal which alternates at the predetermined frequency. This tag requires a relatively high magnetic field level for activation and deactivation. Activation and deactivation is accomplished by exciting a coil wound around a magnetic core.
Some effort has been made to combine an RFID device and an EAS device within a single device. U.S. Pat. No. 7,109,867 to Forster describes a device that includes both an RFID device and an EAS device. U.S. Pat. No. 7,002,475 to Brady describes an RFID tag that includes a non-linear magnetic material in its antennas, allowing it to function also as an EAS device. Both of these combinations involve additional structural elements to perform the two functions in the same device.
From the forgoing it will be appreciated that improvements are possible for RFID devices.